The neutral gear disengages all gears in the transmission and disconnects the transmission from the wheels, allowing the wheels to roll without using the power of the engine. It also closes the neutral safety switch and completes the circuit in the starter relay to allow the car to start.
The neutral gear is used for starting the engine and parking, especially if the vehicle does not have a parking gear selection. It is dangerous and not recommended to put a car in neutral when it is in motion, particularly when it is moving downhill. Since the transmission is disconnected from the driving wheels, the driver cannot use the accelerator or maneuver sharp corners to avoid an accident.